If your grandmother wants to bet her savings on a bundle of credit derivatives, it'll be easy for her to do so through a new swath of exchange-traded funds (ETFs).

The ETFs may not have been created with her in mind, but she'll be able to buy their shares. Regulators this month signed off on a plan to allow trading in eight new ProShares ETFs backed by wagers on the creditworthiness of the riskiest to the safest corporate borrowers. Those funds, which package credit-default swaps, join more than 250 others that are based on derivatives, an arena traditionally dominated by hedge funds.

The reality is that while anyone can invest in these ETFs, which provide easy access to harder-to-trade, privately negotiated markets, the target demographic is probably institutional investors. They are a growing presence among buyers of fixed-income ETF shares, which trade on exchanges like stocks and are backed by everything from Treasuries to below-investment-grade loans.